Yoga Sūtra Chapter Four verse 2
jāti-antara-pariṇāmaḥ prakṛti-āpūrāt ||2||
The transformation into other existences
is due to the flow from the process of matter.
Commentaries and Reflections
Commentary by S Ramaswami:
The question taken up here is the transformation of one level of being to another, i.e. Man to Deva.
It is possible for one being to become another being over the next life.
This relates to the concept of transmigration.
How it takes place, is discussed in this Sūtra.
This change is purely by the new life being filled up by Prakṛti.
There is no change in Puruṣa.
The process is obviously very subtle.
The new Janma is a rearrangement of Prakṛti.
It is possible to either go higher up or lower down:
i.e. Nandi to a celestial bull by Śiva
i.e. Nahuṣa to a serpent by Agastya.
Having assumed this, and that the transmigration is either Sattva or Tamas, why is this?
Your actions produce.
Vyāsa says causes such as virtue or Dharma, or its opposite unvirtuous or Adharma indirectly change the flow of Prakṛti.
This is explained in the next Sūtra.